I have an array of Float (representing audio samples) and I want to turn it into an AVAudioPCMBuffer so I can pass it to AVAudioFile's write(from:). There's an obvious way (actually not obvious at all, I cribbed it from this gist):
var floats: [Float] = ... // this comes from somewhere else
let audioBuffer = AudioBuffer(mNumberChannels: 1, mDataByteSize: UInt32(floats.count * MemoryLayout<Float>.size), mData: &floats)
var bufferList = AudioBufferList(mNumberBuffers: 1, mBuffers: audioBuffer)
let outputAudioBuffer = AVAudioPCMBuffer(pcmFormat: buffer.format, bufferListNoCopy: &bufferList)!
try self.renderedAudioFile?.write(from: outputAudioBuffer)
This works (I get the audio output I expect) but in Xcode 13.4.1 this gives me a warning on the &floats: Cannot use inout expression here; argument 'mData' must be a pointer that outlives the call to 'init(mNumberChannels:mDataByteSize:mData:)'
Ok, scope the pointer then:
var floats: [Float] = ... // this comes from somewhere else
try withUnsafeMutablePointer(to: &floats) { bytes in
let audioBuffer = AudioBuffer(mNumberChannels: 1, mDataByteSize: UInt32(bytes.pointee.count * MemoryLayout<Float>.size), mData: bytes)
var bufferList = AudioBufferList(mNumberBuffers: 1, mBuffers: audioBuffer)
let outputAudioBuffer = AVAudioPCMBuffer(pcmFormat: buffer.format, bufferListNoCopy: &bufferList)!
try self.renderedAudioFile?.write(from: outputAudioBuffer)
}
The warning goes away, but now the output is garbage. I really don't understand this as floats.count and bytes.pointee.count are the same number. What am I doing wrong?
ratkins
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